In high speed packaging, weighing and labelling operations, after the step of wrapping a product such as meat or poultry for sale in a supermarket, the next requirement is for that product to be weighed and labeled. If the product happens to be one with a flat bottom or one supported in a tray, it tends to function smoothly in a conveyorized operation. If it is a product that does not have a flat bottom, such as a whole bird poultry product or is another type of product having an irregular surface on which the product typically rests while being conveyed, the swift movement of a conventional flat horizontal conveyor may induce oscillation or wobble in the product while being conveyed. The reason for this is that in modern conveyorized packaging operations, the products can be processed at speeds of 70 or more pieces per minute. That amount of speed will frequently jolt a whole bird poultry product such that it rocks on its non-flat bottom and begins to wobble.
Wobble or oscillation by itself may not present a problem if it is being transported merely to get to a destination, but when the purpose of the transport is to weigh and label the bird, unreliability and inaccuracy will most likely occur. A wobble in the weighing operation will result in an incorrect weight. A wobble in the labelling operation will result in an improperly positioned label. In addition, the wobble on a flat open conveyor belt frequently results in an orientational misalignment of the product, further disturbing label location.
The conventional conveyor is one which has a basically flat horizontal belt, or similar supporting surface, and transports the product through the operative stations. In the case of a multiple process sequence, typically entry, weighing, and labelling, the conveyor system may be a series of short conveyors working in sequence. Such a multiple sequence conveyor apparatus for weighing and labelling is exemplified by the HI 2600 apparatus made by New Brunswick International, Inc. of Lilburn, Ga. Wobble is very likely to occur in this sort of system when the product does not have a flat bottom especially because the product will be transferred from one belt to another across a depression or gap, thus inducing a vibration or oscillation.
While the referred to type of multiple process conveyor equipment is more reliable for weighing a product which is in a tray, since it will not wobble, there is an additional drawback. Since the entire movement of the product relies on friction with the conveyor surface, the consistency of that frictional contact controls the consistency of positioning of the label. If there is grease on the surface of either the conveyor or the product, or a difference in the weight of the product, thereby affecting the frictional drive, there could be a variation in the position of the product at the time the label is applied due to slippage. At the operating speeds common today of 70 or more pieces per minute, an individual product is on each station of the apparatus less than one second. A signal is generated prior to the time the product reaches the labelling station so that the label will be propelled to intercept the product at the right time. Unless the product moves forward at a known speed, the label may be applied differently from item to item. Naturally, the more uniform the label placement, the more acceptable the product. This situation is exacerbated by a design feature of many current conveyor weighing devices which, in order to separate items so only one is at the weighing station at a time, will run the three sections at successively increased speeds.
The problem described above is dealt with in applicant's U.S. Pat. No. 5,086,855 and the related divisional U.S. Pat. No. 5,137,099 the teachings of which are incorporated herein by reference. The '855 patent discloses an apparatus having a three-station conveyor, each station including a pair of vertically oriented product control belts. While the solution presented in the '855 patent avoids product wobble, it has been discovered that a vertical belt system mounted on the weighing station induces a degree of electromagnetic noise which distorts the weighing accuracy.
As used in the following description and claims, a "non-flat" bottom refers to a bottom surface of a product on which the product rests and which supports the product in a manner which is somewhat unstable and may tend to permit the product to wobble on a conveyor.
Therefore, an object of the present invention is to improve the accuracy and reliability of weighing of conveyor weighed products with non-flat bottoms.
A further object of the present invention is to improve the label placement accuracy of products labeled in a conveyorized operation.
An additional object of the present invention is to maintain better control of the products being weighed and labelled at current process speeds and further increased speeds likely to occur in the near future.
Other objects will become apparent as the description proceeds.